The present invention relates to packaging for products, such as fresh red meat or other food products, that are enclosed between a support member and a film, wherein the film can be peelably delaminated to alter its gas-permeability, thereby changing the environmental conditions within the package. More specifically, the invention relates to a method and apparatus for producing such packaging and providing the film with a tab to facilitate the peelable delamination thereof.
Various forms of packaging, particularly for food products, employ a relatively rigid support member, such as a flat sheet or tray, upon or in which a product is supported. The product is typically covered by a relatively flexible, transparent film. The film is bonded to the support member around the product, generally by forming a heat-seal between the film and support member, to thereby enclose the product between the film and support member. Examples of this type of packaging include vacuum skin packaging and modified-atmosphere packaging.
In vacuum skin packaging, the film is thermoformable, i.e., capable of being formed into a desired shape upon the application of heat, and is thermoformed about the product on a support member by means of heat and differential pressure. Virtually all of the air is evacuated from the interior of the package so that the film conforms very closely to the contour of the packaged product. Generally, sufficient heat is applied to cause the film to bond with the support member outside the periphery of the product, either by employing a heat-activatable adhesive at the interface of the film and support member or by forming the film and support member from materials that are otherwise sealingly compatible upon the application of heat, e.g., by employing similar polymeric materials, such as polyethylenes, at the seal interface that bond to one another when heated. Alternatively, a pressure-sensitive adhesive can be used. Further details are described in, e.g., U.S. Pat. Nos. Re 30,009 (Purdue et al.), 5,346,735 (Logan et al.), and 5,770,287 (Miranda et al.), the disclosures of which are hereby incorporated herein by reference.
In modified-atmosphere packaging, a food product is generally packaged in a tray-like support member having a peripheral flange to which the film is secured. Prior to securing the film to the support member, air is generally evacuated from the interior of the support member and replaced by a gas which extends the shelf-life of the packaged product.
In these and similar types of packaging applications, both the film and support member generally comprise materials which form a barrier to the passage of gas therethrough so that the package is, at least initially, substantially gas-impermeable. Eventually, a portion of the film is removed by a retailer prior to placing the package in a display case for consumer purchase. The latter event occurs where it is desirable to increase the gas-permeability of the film in order to allow air (oxygen) to come into contact with the packaged product while still providing protection to the product from, e.g., dirt, dust, moisture, and other contaminates. This is generally desirable where air-contact with the packaged product renders the product more appealing to the consumer in some way.
For example, while a low-oxygen packaging environment generally increases the shelf-life of a packaged fresh red meat product (relative to meat products packaged in an environment having a higher oxygen content), red meat has a tendency to assume a purple color when packaged in the absence of oxygen or in an environment having a very low oxygen concentration, i.e., below about 5% oxygen. Such a purple color is undesirable to most consumers, and marketing efforts to teach the consumer about the acceptability of the purple color have been largely ineffective. When meat is exposed to a sufficiently high concentration of oxygen, e.g., as found in air, it assumes a bright red color which most consumers associate with freshness. After 1 to 3 days of such exposure, however, meat assumes a brown color which, like the purple color, is undesirable to most consumers (and indicates that the meat is beginning to spoil). Thus, in order to effectively butcher and package fresh red meat products in a central facility for distribution to retail outlets, the meat is packaged, shipped, and stored in a low-oxygen (vacuum or modified-atmosphere) environment for extended shelf-life, and then displayed for consumer sale in a relatively high-oxygen environment such that the meat is caused to "bloom" into a red color just before being placed in a retail display case.
The foregoing may be accomplished by providing a film that peelably delaminates into a gas-permeable portion and a substantially gas-impermeable portion, with the gas-permeable portion being bonded to the support member so that the gas-impermeable portion can be peelably removed from the package. In this manner, the package may be shipped with the upper, gas-impermeable portion secured to the lower, gas-permeable portion to maintain a low-oxygen environment within the package during shipping. Then, the gas-impermeable portion may be peelably removed at the supermarket just prior to placing the package in a retail display case. Since the remaining portion of the film is permeable to gas (oxygen), it allows the meat product to bloom in the presence of oxygen which enters the package from the ambient atmosphere. This general packaging concept is also applicable to poultry, which assumes a pink color in the presence of oxygen but has a longer shelf-life in a low-oxygen environment, as well as to other perishable foods such as cheese and produce.
Regardless of the particular type of peelable package that is employed, e.g., a vacuum skin package or modified-atmosphere package, it is desirable that the film have a tab which can be manually grasped to facilitate peeling and removal of the gas-impermeable portion from the gas-permeable portion. Such a peel tab would desirably be provided without the need to add additional components to the package, and would also be provided in the same process in which the package is made, i.e., without the need for a separate "off-line" process. It would also be desirable for the package having such a peel tab to be aesthetically appealing both prior to and after peelable delamination of the film.